Aerosol type dispensers have been in wide use for many years. The most commonly used type has a container in which is contained a fluent material to be dispensed. By fluent material is meant a material which will flow when subjected to the pressure of the propellant, such as a liquid or a powder. In a very common arrangement, in the space within the container above this material is a pressurized propellant vapor, such as Freon or the like, which exerts a pressure on the fluent material. A dip tube extending downwardly into the container and having a valve means at the top thereof, normally pushbutton actuated, acts as a control to release the fluent material, which is forced through the dip tube from the interior of the container by the pressure of the propellant on the upper surface of the fluent material. In another arrangement the fluent material is contained in a collapsible sac in place of the dip tube, and the propellant surrounds the sac and presses material out of the sac. Many proposals have been made for modifying or adding to such dispensers to make them capable of dispensing more than one fluent material.
In order that such dispensers operate properly, a relatively high pressure is required, on the order of 60 psig (about 4 Kg/cm.sub.2 above ambient). While this produces relatively good atomization of the fluent being dispensed, it has the major disadvantage that the container or containers for the fluent materials must have sufficient strength to withstand this pressure within the container. This requires that special precautions, with consequent added cost, must be taken during the shipment and storage of the containers. Most of the containers carry a warning that they should be punctured before being disposed of after they have been used so as to avoid the likelihood of an explosion should the cans with only some propellant under pressure remaining in them be incinerated.
It would be highly desirable if the pressure of the propellant within the container or containers in such multi-fluent material dispensing devices could be reduced without having any detrimental effect on the quantity and the fineness of the spray of fluent materials, being dispensed. This would reduce the cost of making the containers, and it would greatly simplify and make much less dangerous the transportation, storage and disposal of containers during and after their use.